Women should be banned from having abortions after as little as 12 weeks of pregnancy, halving the current legal limit, according to Tory leadership contender Liam Fox.

The move would affect more than 24,000 women a year in Britain, where terminations are currently allowed up to 24 weeks - potentially forcing them either to have an unwanted child or travel abroad for the procedure.

Asked if women should be prevented from having more than one abortion on the NHS to stop them taking the issue too lightly, the former doctor said that he had not gone into politics 'to make it easier for people to abort their unborn children'.

The remarks from Fox, who is lagging behind the two frontrunners in the contest, thrust abortion firmly back on to the political agenda. David Cameron and David Davis's camps made clear yesterday that both men support lowering the limit, but only to 18-20 and 20 weeks respectively. Kenneth Clarke declined to comment, but has previously opposed lowering the limit.

The remarks came as it emerged that Britain's biggest abortion provider will this week be cleared of breaking the law in facilitating abortions abroad for pregnant women who have passed the current 24-week cut-off point in Britain.

The verdict from Professor Sir Liam Donaldson, chief medical officer on the British Pregnancy Advisory Service, is a serious blow to pro-life campaigners and means that women seeking controversial very late terminations can still do so if they are willing to travel. The inquiry follows reports from an undercover journalist that the BPAS arranged for her to have an abortion in Spain at 26 weeks' pregnant.

Late abortions have become a controversial issue. Some doctors argue the current limit is inappropriate now that premature babies born at 24 weeks increasingly survive: others, however, say most late abortions are for previously undetected serious defects and that reducing the limit would put intolerable pressure on mothers.

Fox said he wanted to see the time limit brought down to 20 weeks then 'serially' much lower.

'I would like to see us looking at limits more akin to some of the European countries at 12, 14 weeks,' he told Channel 4's Morgan and Platell programme last night. 'A society that actually aborts 180,000 unborn children every year is a society that needs to be asking a lot of questions about itself.'

A spokesman for Fox said he did not intend to make abortion a campaign issue. Fox also became the first candidate openly to criticise Clarke's directorship of British American Tobacco.

Asked whether he thought the link was damaging, Fox said: 'I think that the tobacco industry - knowing the health risks associated with it, making profits out of selling tobacco into the Third World - has a big moral question mark over it.'